Device and method of detecting magnetic characteristic change for long material

Abstract

A device of detecting magnetic characteristic change for a long material includes: an exciting coil into which the long material is inserted and which magnetizes the long material in a longitudinal direction; a detecting coil into which the long material is inserted and which detects a magnetic flux generated in the long material due to magnetization by the exciting coil; and a yoke member which has a first opening portion which is positioned on one side of the long material in the longitudinal direction and into which the long material is inserted and a second opening portion which is positioned on the other side of the long material in the longitudinal direction and into which the long material is inserted, and has a shape which is substantially axially symmetrical about an axis passing the first opening portion and the second opening portion, and the exciting coil and the detecting coil are surrounded by the yoke member, the first opening portion, and the second opening portion.

Description

[0001]Priority is claimed on PCT / JP2017 / 039076 filed on Oct. 30, 2017, the content of which is incorporated herein by reference.BACKGROUND OF THE INVENTIONField of the Invention[0002]The present invention relates to a device and a method of detecting magnetic characteristic change for a long material, which detect portions where magnetic characteristics change in the long material.Description of Related Art[0003]It has been known that in a case where poor quenching is partially caused in a heat treatment of a steel pipe (hereinafter, referred to as “pipe”) which is an example of a long material, magnetic characteristics change in the part where the poor quenching is performed. Using this characteristic, a state of the heat treatment performed on the pipe can be recognized by measuring the magnetic characteristics of the pipe.[0004]FIG. 1A is a diagram briefly showing a measurement method using a test piece, which has been known as the most usual method of measuring magnetic characte...

AI Technical Summary

Benefits of technology

The invention allows for the reduction of a dead zone at the end of a long material and accurately detects areas where magnetic characteristics change over the entire length of the material.

Problems solved by technology

However, in a case of the measurement method shown in HG 1A, pipes are required to be cut into short pieces in a longitudinal direction and the pipes after the cutting cannot be dealt with as products.

Accordingly, all pipes cannot be inspected.

Accordingly, it is thought that it is difficult to detect a poorly quenched portion generated in a part of a cross-section based on a difference in the magnetic characteristics between a normal quenched portion and the poorly quenched portion.

In other words, there is a problem in that a region where the measurement cannot be performed (dead zone) exists in the end portion of the steel material in the longitudinal direction.

In addition, in a case where the device (device using the measurement head provided with the external magnetic circuit and the detecting coil) described in FIG. 11 in Patent Document 1 is applied to the detection of portions where magnetic characteristics change of the material characteristics of the pipe which is relatively moved in the longitudinal direction change, there is a concern that a scratch may occur on an outer surface of the pipe in a case where the yoke member (contact core) constituting the external magnetic circuit is brought into contact with the pipe.

Accordingly, in a case where the variation of pass-line is large, the value which is measured by the detecting coil also varies, and thus there is a problem in that magnetic characteristics of the necessary pipe cannot be accurately detected over the whole length thereof.

Accordingly, with the method described in Patent Document 2, a poorly quenched portion generated in a part of a cross-section cannot be accurately detected.

Accordingly, with the method described in Patent Document 3, a poorly quenched portion generated in a part of a cross-section cannot be accurately detected.

This problem is also common to other long materials such as a steel bar.

In addition, in the above description, a heat treatment is used as an example of a cause of the material characteristic change, but a similar problem may be caused due to a cause other than the heat treatment, such as the magnitude of hardening accompanying the processing or a change in the carbon amount accompanying decarburizing or carburizing.

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